When processing semiconductor wafers, it is necessary to deposit materials onto and remove materials from the semiconductor wafers. The transfer of material onto and from the semiconductor wafers is used to enhance the electrical properties of the semiconductor wafers. In order to transfer materials onto and from the semiconductor wafers, various gases are used to impinge the semiconductor wafers. For example, to remove contaminants from the semiconductor wafers, a processing gas can be used to contact the semiconductor wafers, and react with the contaminants thereon. However, before such processing can occur, the semiconductor wafers must be provided in a low pressure environment. Therefore, vacuum processing systems are used to remove the semiconductor wafers to a low-pressure environment.
These vacuum processing systems employ a load-lock chamber and vacuum pumps. For example, the semiconductor wafers are placed in the load-lock chamber, and the load-lock chamber is subsequently evacuated using the vacuum pumps. After evacuation, the semiconductor wafers are provided in a low pressure environment, and can thereafter be subjected to further processing.
A dry vacuum pump can be used to evacuate the load-lock chamber to a low pressure. Generally, the cost of pumping the interior of the load-lock chamber to a low pressure is related to five parameters: (1) the amount of gas to be evacuated; (2) the interior surface area of the load-lock chamber; (3) the low pressure required in the load-lock chamber; (4) the resistance in the piping between the load-lock chamber, and the dry vacuum pump; and (5) the time required for providing the low pressure in the load-lock chamber.
Another cost is related to the number of semiconductor wafers each load-lock chamber is capable of processing at one time. Therefore, to reduce the cost of pumping the interior of the load-lock chamber to a low pressure, some have increased the number of semiconductor wafers processed at a time. However, to accommodate the increased number of semiconductor wafers, the size of the load-lock chamber must also be increased. Therefore, such “batch” processing significantly increases the amount of gas to be evacuated and the interior surface area of the load-lock chamber.
Consequently, there is a need to reduce the cost of pumping the interior of the load-lock chamber to a low pressure without the need to resort to “batch” processing. By reducing or eliminating the resistance in the piping between the load-lock chamber and the dry vacuum pump, it is possible to reduce the costs of pumping without the need for resorting to “batch” processing.